M. J. Dauncey is a researcher who developed methods for measuring human energy use with calorimetry. A 1978 study with collaborators described an instrument combining direct calorimetry with an open-circuit indirect calorimetry system for continuous observations lasting at least 24 hours.[ref]
A human calorimeter for the direct and indirect measurement of 24 h energy expenditure by M. J. Dauncey and others. Abstract: continuous heat-production/heat-loss measurements and combined methods
The direct system removed heat through a water-cooled heat exchanger. Control of the wall temperature minimized the mean temperature difference across the chamber walls. Evaporative heat loss was inferred from incoming and outgoing wet-and-dry-bulb temperatures together with air volumetric flow rates.[ref]
For a dimensional example, a steady heat-loss rate of over one hour corresponds to , or . These are illustrative values. Heat loss and metabolic heat production need not match instantaneously if the body is warming or cooling, which motivates measuring complementary quantities over a defined interval.
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